feat: add AI Digital Employee agent orchestrator with pipeline tracking

- New AgentPipeline model with JSONB pipeline_data for stages/leads/summary
- AgentOrchestrator service chains DiscoveryService search→analyze→outreach→auto-save
- 3 new API endpoints: POST /agent/start, GET /agent/pipelines, GET /agent/{id}
- Full Agent dashboard Vue component with stats, pipeline grid, leads table, outreach preview
- Sidebar redesigned with AI Agent as primary entry point
- Updated PROGRESS.md, AGENTS.md, DATABASE_SCHEMA.md with latest state

user-frontend/src/api/index.js

@@ -131,4 +131,8 @@ export function subscribeCreditPlan(planId, payType = 'alipay') {
 }
 export function cancelCreditSubscription() { return http.post('/credits/cancel-subscription') }
 
+export function startAgentPipeline(data) { return http.post('/agent/start', data, { timeout: 300000 }) }
+export function listAgentPipelines(params) { return http.get('/agent/pipelines', { params }) }
+export function getAgentPipeline(id) { return http.get(`/agent/${id}`) }
+
 export default http